Great Tang: The Divine-Level Brat

Li Chengfeng, a scientific genius from the 21st century, transmigrates to the Tang Dynasty, only to become the six-year-old son of Li Shimin! Blessed with the Divine Brat System, Li Chengfeng tugs on Li Shimin's beard and tears into Fang Xuanling and Du Ruhui from the start, leaving them utterly helpless. Using his genius-level scientific knowledge, he solves a natural disaster with a South-to-North Water Diversion project, then develops hybrid rice that yields 2,000 jin per mu. He crushes the Turks and subdues Goguryeo, and at just six years old, Li Chengfeng is granted the title of Divine King Who Guards the Tang. Truly, there's no need to worry about having no friends ahead: who in the world doesn't know you?